The invention relates to a method for determining a fuel mass of a pre-injection that is injected into at least one combustion chamber of a combustion engine as well as a device for implementing the method according to the category of the independent claims.
For operating modern combustion engines, in particular self-injecting diesel motors a highly accurate metering of the fuel mass is required at very high injection pressures. The precision of the controlled fuel metering is however limited at modern injection systems by the manufacturing accuracy on the one hand and characteristics of the components of the injection system that change over the life time of the combustion engine on the other hand, in particular drift appearances, which for example cause increased tolerances. The achievable accuracy is now often not sufficient in order to comply with motoric requirements. Particularly inaccuracies of the pre-injection cause significantly increased emissions depending on the operating point, for example in partial load operation, or conspicuous and therefore annoying combustion noises. Therefore there is an interest in knowing the injected fuel amount very accurately and in particular the deviations of the actual injection amount that actually occurs during the operation of the combustion engine from the desired injection amount, in order to carry out corresponding corrections of the controlling of the injection valves and thus to be able to ensure a correct injection amount.